Vulcanization composition having reduced allergenic potential, and elastomeric articles formed therewith

ABSTRACT

The present invention generally relates to vulcanization compositions used to vulcanize elastomeric articles, where the vulcanization compositions have reduced allergenic potential as compared to elastomeric articles formed using vulcanization compositions having non-fugitive accelerators. The present invention also relates to elastomeric articles formed using the vulcanization compositions. The invention further relates to methods for making a reduced-allergenicity vulcanization composition, and to methods for using the vulcanization compositions to vulcanize elastomeric articles.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a divisional of application Ser. No. 14/993,532, nowU.S. Pat. No. 9,550,906, which is a divisional of application Ser. No.14/617,296, now U.S. Pat. No. 9,260,623, which is a divisional ofapplication Ser. No. 13/169,872, now U.S. Pat. No. 8,980,391 and claimspriority to U.S. Provisional Application No. 61/358,721 titled“Vulcanization Accelerator Composition Having Reduced AllergenicPotential, And Elastomeric Articles Formed Therewith” filed Jun. 25,2010, the entirety of which is hereby incorporated by reference herein.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention generally relates to vulcanization compositionsincluding accelerator compositions used to vulcanize elastomericarticles, where the vulcanization compositions have reduced allergenicpotential as compared to elastomeric articles formed using conventionalvulcanization compositions. The present invention also relates topolychloroprene-based elastomeric articles formed using thevulcanization compositions. The invention also relates to methods formaking a reduced allergenicity vulcanization composition, and to methodsfor using the vulcanization compositions to vulcanize elastomericarticles. According to some aspects the vulcanization compositions mayinclude sulfur, the accelerator compositions, and an activatorcomposition. According to another aspect, the accelerator compositionsmay include a fugitive vulcanization accelerator and the activatorcomposition may include zinc oxide. According to further aspects, theelastomeric articles may include gloves, finger cots, catheters, andcondoms.

2. Description of Related Art

There are two types of allergies associated with the use of elastomericarticles in the medical field: (a) Type I immediate hypersensitivity,IgE-mediated allergies; and (b) Type IV delayed hypersensitivity,cell-mediated allergies.

Type I hypersensitivity reactions are mediated by IgE immunoglobulin,and the effect is immediate. Generally, symptoms are evident withinminutes of exposure to the allergen, and may include local urticaria,facial swelling, watery eyes, rhinitis, asthma, and in extremely rareoccasions, anaphylactic shock. Type I allergies have been linked to theresidual, extractable proteins present in natural rubber latex products.

Various technologies are available for reducing the extractable proteinsin latex gloves, such as water leaching, chlorination, and the use oflow-protein or deproteinated latex. However, healthcare personnel andpatients who are allergic to natural rubber latex proteins are advisedto use synthetic gloves. Commonly-used synthetic materials includepolyisoprene, acrylonitrile-butadiene (nitrile), polychloroprene(Neoprene), polyurethane, and polyvinyl chloride.

As a result of the prevalence of Type I reactions in response to contactwith natural rubber proteins, there has been a shift towards the use ofsynthetic latexes that do not contain natural rubber latex proteins,especially for use in making medical devices that come into contact withthe skin. Taking cost and performance into consideration, syntheticlatexes that are suitable for glove manufacture include nitrile latexand polyurethane latex for examination gloves, and polychloroprene latexand polyisoprene latex for surgical gloves. For surgical gloves,polyisoprene latex has typically been preferred over polychloroprene,even though it is more expensive, because it provides the gloves withproperties that mimic those of natural rubber, particularly tensilestrength, ultimate elongation, softness and comfortable feel.

However, Type IV allergic reactions can be caused by natural orsynthetic elastomeric articles. Synthetic latexes can still causeallergic reactions due to the use of certain chemicals that may be foundin the compounded latex. Type IV delayed hypersensitivity reactions arecell-mediated allergic responses to specific chemicals. Symptoms onlybecome apparent about 48-96 hours after contact. Chemicals that mayinduce Type IV allergic responses include vulcanization acceleratorssuch as thiurams, mercaptobenzothiazoles, dithiocarbamates,diphenylguanidines, and thioureas, which are used in the process ofpreparing the elastomeric articles. The U.S. Food and DrugAdministration (FDA) acknowledges that thiazoles, thiurams, andcarbamates in rubber products can induce Type IV allergic reactions inhumans. “Guidance for Industry and FDA Reviewers/Staff: PremarketNotification [510(k)] Submissions for Testing for Skin Sensitization toChemicals in Natural Rubber Products,” U.S. Department of Health andHuman Services (1999). Hence, it is important to minimize the level ofaccelerators used so that the residual accelerator in the finishedelastomeric article is very low.

Elastomeric articles are generally manufactured using a latex dippingprocess, which involves dipping molds or formers into a coagulantsolution (usually aqueous calcium nitrate). After evaporating off thesolvent, the coagulant-coated molds/formers are then dipped intocompounded latex such that a film of coagulated rubber particles isdeposited thereon. After gelling the latex film using heat, thewet-gelled latex film is leached in water and then dried and vulcanizedin a hot air oven. During vulcanization the rubber molecules arechemically crosslinked.

Most commonly, the crosslinking agent is sulfur. However, sulfur aloneis inefficient for forming crosslinks. Conventionally, sulfur has alwaysbeen used in combination with vulcanization accelerators and activators.

Vulcanization accelerators are usually organic compounds that increasethe rate and efficiency of sulfur crosslinking, while activators arecompounds that increase the efficiency of the accelerators. Examples ofaccelerators used in latex compounding include thiurams,dithiocarbamates, mercaptobenzthiazole, diphenylguanidine, andthioureas. After vulcanization, depending on the amount of theaccelerator used, some or most of the accelerators are chemically bondedto the rubber matrix, but some are unreacted and may remain as a residuein the finished elastomeric article.

Vulcanization activators used in latex compounding are usually metaloxides, such as zinc oxide, magnesium oxide, and lead oxide.

Various methods for minimizing or eliminating Type IV allergic reactionscaused by vulcanization accelerators have been attempted, includingcrosslinking without the use of sulfur and vulcanization accelerators.Approaches include (a) crosslinking using gamma irradiation, (b)crosslinking using organic peroxides, (c) crosslinking using zinc oxidealone, via carboxyl-zinc ionic bonding, and (d) introducing functionalgroups into the polymer backbone that can form crosslinks after theproduct has been fabricated. Generally speaking, all of these approachessuffer from drawbacks. For example, approaches (a) and (b) result inproducts having poorer physical properties and poorer aging resistancethan sulfur-vulcanized products.

Another approach is the use of safer accelerators. These areaccelerators that have a lower allergenic potential. For example, ahigh-molecular weight accelerator that has low allergenic potential maybe used, including, e.g., zinc dibenzyl dithiocarbamate (ZBEC), and zincdiisononyl dithiocarbamate (ZDNC). By virtue of their high molecularweights, these types of accelerators are more compatible with naturalrubber and synthetic polyisoprene rubber, and therefore have a highersolubility in the rubber matrix. As a result, very little of thehigh-molecular weight accelerator would bloom to the rubber surface andcome in contact with the user to cause a potential allergic reaction.For the same reason, very little of the high-molecular weightaccelerator can be extracted from the rubber. ZDNC is preferred overZBEC because it has a higher solubility in natural rubber (about 3%weight/weight), whereas the solubility of ZBEC is only about 0.5%weight/weight.

A further approach is to use combinations of fugitive accelerators,i.e., accelerators that are completely used up during vulcanization,leaving no residue in the product. Examples of such fugitiveaccelerators include xanthates, such as diisopropyl xanthogenpolysulfide (DIXP), or dibutyl xanthogen disulfide (DBXD). Heating DIXPalone to high temperatures does not volatalize or decompose itcompletely to gaseous products. However, when DIXP is used together withsulfur and zinc oxide for crosslinking a diene containing polymer orrubber, it is consumed completely to form sulfur crosslinks, isopropanoland carbon disulfide as the major reaction products, leaving behindvirtually no residue on the polymer or rubber since isopropanol andcarbon disulfide would volatilize at the crosslinking/vulcanizationtemperatures. Since DIXP does not contain nitrogen in its chemicalstructure, it is also impossible to generate N-nitrosamines, which areassociated with thiuram and dithiocarbamate accelerators. Additionally,certain nitrosamines are believed to be carcinogenic, and theirformation should be avoided. However, DIXP alone does not acceleratesulfur crosslinking sufficiently to produce enough sulfur crosslinks toyield useful products. The resulting articles have a tensile strengththat is too low. Hence, DIXP has always been used in conjunction withanother accelerator.

A variety of accelerator compositions have been disclosed in the priorart, some of which are discussed below.

U.S. Published Application No. 2003/0161975 discloses the use of sulfurand DIXP, together with tetrabenzyl thiuram disulfide or ZBEC to producepolyisoprene condoms that are defect-free. The latex compound hasimproved stability compared to latexes formed using conventionalaccelerators such as zinc diethyl dithiocarbamate and zinc dibutyldithiocarbamate.

A synergistic combination of DIXP and ZDNC has been recommended as asafer accelerator for use with natural rubber latex and syntheticpolyisoprene latex. Chakraborty et al., “Novel Sustainable Acceleratorsfor Latex Applications—Update,” International Latex Conference (2005).

For vulcanizing polychloroprene, conventional curing packages includesulfur, non-fugitive accelerators, and zinc oxide. Non-fugitiveaccelerators that are used include zinc dibutyl dithiocarbamate (ZDBC);a mixture of tetraethylthiuram disulfide and sodium dibutyldithiocarbamate; and a mixture of diphenyl thiourea (thiocarbanilide)and diphenyl guanidine (see Carl, Neoprene Latex, chapter 3, publishedby E.I., du Pont de Nemours & Co. (1962)). However, residuals of thesenon-fugitive accelerators in the product can induce Type IV allergicreactions.

Chakraborty et al. (2nd International Rubber Glove Conference 2004,Kuala Lumpur, Malaysia) disclosed formulations using sulfur, twocombinations of two accelerators (ZDNC and DIXP, or ZDEC and MBT), zincoxide, and two antioxidants (A02246 and MMBI).

Jole Van (WO 2007/017368) also disclosed formulations using sulfur,accelerators (DIXP and alkyl dithiocarbamates of various chain lengths,such as ZDNC, and DPG), zinc oxide, and an antioxidant (Aquanox L).

Lucas (WO 2003/072340) disclosed formulations using sulfur, accelerators(various combinations comprising DIXP, DIX, XS, TETD, TBeTD, and ZDBeC),zinc oxide, and an antioxidant (Wingstay L).

Sparks et al. (U.S. Pat. No. 3,378,538) discloses a process forpreparing a sulfur-modified polychloroprene by polymerizing in thepresence of sulfur and a dialkyl xanthogen disulphide.

Collette et al. (U.S. Pat. No. 3,397,173) discloses a process forpolymerizing chloroprene and sulfur in an aqueous emulsion to form alatex. The polymerization is conducted in the presence of sulfur,dialkyl xanthogen disulfide, and an antioxidant.

Takeshita (U.S. Pat. No. 4,605,705) disclose a heat-resistant,sulfur-modified polychloroprene copolymer of 2-chloro-1,3-butadiene and2,3-dichloro-1,3-butadiene formed using elemental sulfur, anddiisopropyl xanthogen disulfide or an equivalent amount of a dialkylxanthogen disulfide, such as dibutyl xanthogen disulfide.

Accordingly, there is a need in the art for vulcanization compositionsused to vulcanize elastomeric articles, where the vulcanizationcompositions have reduced allergenic potential as compared toelastomeric articles formed using vulcanization compositions havingnon-fugitive accelerator compositions. The present invention alsorelates to polychloroprene-based elastomeric articles formed using thevulcanization compositions. The invention also relates to methods formaking a reduced allergenicity vulcanization composition, and to methodsfor using the vulcanization compositions to vulcanize elastomericarticles.

SUMMARY OF THE INVENTION

The present invention provides vulcanization compositions havingaccelerator compositions that are used to vulcanize elastomericarticles. The vulcanization compositions have reduced allergenicpotential as compared to vulcanization compositions having non-fugitiveaccelerator compositions, and may be used to form elastomeric articlesthat have reduced allergenic potential as compared to elastomericarticles formed using vulcanization compositions having non-fugitiveaccelerator compositions. Non-fugitive accelerator compositions mayinclude thiazoles, thiurams, carbamates, guanidines, and thioureas. Thepresent invention also relates to polychloroprene-based elastomericarticles formed using the vulcanization compositions. The inventionfurther relates to methods for making a reduced allergenicityvulcanization composition, and to methods for using the vulcanizationcompositions to vulcanize elastomeric articles.

The present invention meets the unmet needs of the art, as well asothers, by providing vulcanization compositions, latex dispersions, andelastomeric articles that exhibit reduced or eliminated allergicpotential as compared to vulcanization compositions, latex dispersions,and elastomeric articles formed using conventional techniques. Accordingto some aspects, the present invention results in reduced or eliminatedType I and Type IV allergenicity. The vulcanization compositions, latexdispersions, elastomeric articles, and methods of the present inventionare beneficial for avoiding problems associated with allergic reactionsto elastomeric articles, particularly in the medical field, where bothhealth care providers and patients are exposed to these potentialsources of allergens frequently and/or for extended periods of time.

According to one aspect of the invention, the invention relates to avulcanization composition comprising sulfur, a single fugitive xanthateaccelerator, and a metal oxide, where the vulcanization composition doesnot include an additional accelerator. According to another aspect ofthe invention, the invention relates to a vulcanization compositioncomprising sulfur, one or more fugitive xanthate accelerators, and ametal oxide, where the composition does not include a non-fugitiveaccelerator. According to some aspects, the vulcanization compositionexhibits reduced allergenicity as compared to vulcanization compositionscomprising non-fugitive accelerators.

According to another aspect of the invention, the vulcanizationcomposition comprises sulfur, diisopropyl xanthogen polysulfide, and ametal oxide, and does not include an additional accelerator. Accordingto another aspect of the invention, the vulcanization compositioncomprises sulfur, diisopropyl xanthogen polysulfide, and a metal oxide,and does not include a non-fugitive accelerator. According to someaspects, the vulcanization composition exhibits reduced allergenicity ascompared to vulcanization compositions comprising non-fugitiveaccelerators.

According to yet another aspect of the invention, the vulcanizationcomposition consists of sulfur, an accelerator composition includingdiisopropyl xanthogen polysulfide, and an activator including a metaloxide. According to some aspects, the accelerator composition exhibitsreduced allergenicity as compared to non-fugitive accelerators.

Still another aspect of the invention provides a latex dispersioncomprising an elastomer and a vulcanization composition comprisingsulfur, a single fugitive xanthate accelerator, and a metal oxide, wherethe composition does not include an additional accelerator. Anotheraspect of invention provides a latex dispersion comprising an elastomerand a vulcanization composition comprising sulfur, one or more fugitivexanthate accelerators, and a metal oxide, where the composition does notinclude a non-fugitive accelerator. According to some aspects, theelastomeric articles exhibit reduced allergenicity as compared toelastomeric articles formed using non-fugitive accelerators. Accordingto further aspects, the elastomer is polychloroprene. According to stillfurther aspects, the latex formulation may be used to form elastomericarticles that may include, but are not limited to, gloves (specificallymedical gloves, and more specifically examination and surgical gloves),as well as condoms, probe covers, dental dams, finger cots, andcatheters.

According to further aspects of the invention, a method of preparing areduced-allergenicity vulcanization composition is provided, in whichsulfur, a single fugitive xanthate accelerator, and a metal oxide arecombined. The method does not include a step of providing an additionalaccelerator composition. According to another aspect of the invention, amethod of preparing a reduced-allergenicity vulcanization composition isprovided, in which sulfur, one or more fugitive xanthate accelerators,and a metal oxide are combined. The method does not include a step ofproviding a non-fugitive accelerator.

According to still further aspects of the invention, a method ofpreparing a reduced-allergenicity elastomeric article is provided, inwhich a latex dispersion is formed that includes vulcanizationcomposition comprising sulfur, a single fugitive xanthate accelerator,and a metal oxide, and the latex dispersion is used to form anelastomeric article. In some aspects, the elastomeric article may beformed by the coagulant dipping method. The method does not include astep of adding another accelerator composition to form the article.According to another aspect of the invention, a method of preparing areduced-allergenicity elastomeric article is provided, in which a latexdispersion is formed that includes a vulcanization compositioncomprising sulfur, one or more fugitive xanthate accelerators, and ametal oxide, and the latex dispersion is used to form an elastomericarticle. The method does not include a step of adding a non-fugitivecomposition to form the article.

Other novel features and advantages of the present invention will becomeapparent to those skilled in the art upon examination of the followingor upon learning by practice of the invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

The present invention generally relates to vulcanization compositionsincluding accelerator compositions used to vulcanize elastomericarticles, where the accelerator compositions have reduced allergenicpotential as compared to elastomeric articles formed using vulcanizationcompositions having non-fugitive accelerator compositions. Thevulcanization compositions comprise sulfur, zinc oxide, and a fugitivevulcanization accelerator. The present invention also relates to latexdispersions and elastomeric articles formed using the vulcanizationcompositions. The present invention further relates to methods formaking a reduced allergenicity vulcanization composition, and to methodsfor using the vulcanization compositions to vulcanize elastomericarticles.

Fugitive vulcanization accelerators for use in accordance with thepresent invention include xanthates. Diisopropyl xanthogen polysulfide(DIXP) and dialkyl xanthogen disulfides are preferred fugitive xanthatesthat may be used in accordance with the present invention, and it isenvisioned that additional fugitive xanthates that may be developed inthe future will also find use in the accelerator compositions, latexdispersions, and elastomeric articles of the present invention. Fugitivexanthates are useful in the accelerator compositions of thevulcanization compositions of the present invention because duringvulcanization they are consumed by bonding to the rubber matrix, andform gases and/or volatile liquids as by-products that evaporate,thereby leaving no residue on the elastomeric article. In the case ofdiisopropyl xanthogen polysulfide (DIXP), the compound form isopropylalcohol and carbon disulfide gas as by-products.

The present invention also provides elastomeric articles made frompolychloroprene rubber and vulcanized using sulfur, zinc oxide, andDIXP. According to some aspects, the elastomeric articles may includegloves (specifically medical gloves, and more specifically examinationand surgical gloves), as well as condoms, probe covers, dental dams,finger cots, and catheters. According to certain aspects polychloroprenesurgical and examination gloves made using such an acceleratorcomposition are provided.

Elastomeric articles made using non-fugitive accelerator compositionscontain residual accelerators that could cause Type IV allergy reactionsin humans, and elastomeric articles made using natural rubber containextractable latex proteins that are linked to Type I allergy reactionsin humans. Because the elastomeric articles, accelerator compositions,latex compositions, methods of making accelerator compositions, andmethods of vulcanizing elastomeric articles in accordance with thepresent invention do not incorporate natural rubber, and do not haveresidual accelerators included therein, the potential for Type Iallergic reactions and Type IV allergic reactions is reduced oreliminated. Non-fugitive accelerator compositions may include thiazoles,thiurams, carbamates, and the like, which are known to cause Type IVallergy reactions in humans. Other non-fugitive accelerators such asguanidines and thioureas have also been used in rubber gloves.

The compositions and methods of the invention will be described ingreater detail below.

Vulcanization Compositions

The vulcanization compositions of the present invention preferablyinclude a source of sulfur, an accelerator composition, and anactivator. The accelerator compositions may include a fugitiveaccelerator. According to certain aspects of the invention, in which theallergenicity of the vulcanization composition is being minimized oreliminated, elemental sulfur and a single xanthate fugitive acceleratorare used. In another aspect elemental sulfur and one or more xanthatefugitive accelerators are used and a non-fugitive accelerator is notincluded. The accelerator is in a range from about 0.1 to about 10 partsby dry weight rubber, preferably from about 0.5 to about 5 parts by dryweight rubber, and more preferably about 1 to about 4 parts by dryweight rubber. The vulcanization compositions may be used to vulcanizeelastomers including natural rubber, polyurethane, polybutadiene,polychloroprene (Neoprene), nitrile rubber, block copolymers of styreneand butadiene, block copolymers of styrene and isoprene, andpolyisoprene. In certain preferred aspects of the invention, theelastomer is polychloroprene.

In aspects of the invention in which the allergenicity of thevulcanization composition is being minimized or eliminated altogether,the source of sulfur used in the vulcanization composition compriseselemental sulfur. According to certain aspects of the invention, onlyelemental sulfur is used.

The vulcanization activator may include, but is not limited to, zincoxide, magnesium oxide, lead oxide, and combinations thereof. Zinc oxideis used as a vulcanization activator in certain aspects of theinvention. The activator is in a range from about 0.1 to about 15 partsby dry weight rubber, preferably from about 6 to about 12 parts by dryweight rubber, and more preferably from about 5 to about 13 parts by dryweight rubber.

In aspects of the invention in which the allergenicity of thevulcanization composition is being minimized or eliminated altogether,the vulcanization accelerator used in accordance with aspects of theinvention is a fugitive xanthate. According to some aspects, thefugitive xanthate is a polysulfide that includes more than two sulfidegroups, i.e., three or more sulfide groups (trisulfide), four or moresulfide groups (tetrasulfide), five or more sulfide groups(pentasulfide), etc. According to further aspects of the invention, thefugitive xanthate is diisopropyl xanthogen polysulfide (DIXP) or adialkyl xanthogen disulfide, such as dibutyl xanthogen disulfide, anddiisopropyl xanthogen disulfide. It should be noted that these fugitivexanthate accelerators can also serve as sulfur donors. In an aspect ofthe invention, the sulfur donor has a low allergenic potential. Theelemental sulfur or sulfur donor is in a range from about 0.1 to about 5parts by dry weight rubber, preferably from about 0.5 to about 2 partsby dry weight rubber, and more preferably from about 1.2 to 1.5 parts bydry weight rubber.

In certain aspects of the invention, only a single fugitive xanthatevulcanization accelerator is used in the accelerator composition, andany additional vulcanization accelerators are excluded from theaccelerator composition. In another aspect one or more fugitive xanthateaccelerators may be used, and a non-fugitive accelerator is not used.

According to further aspects of the invention, DIXP is used as the solevulcanization accelerator, and is the only compound that functions as avulcanization accelerator that is included in the acceleratorcomposition. When accelerator compositions having reduced or eliminatedallergenicity are prepared in accordance with the present invention,they may beneficially comprise only DIXP as a fugitive accelerator. Anyadditional compounds that may also function as vulcanizationaccelerators are excluded from the accelerator compositions. In anotheraspect, additional fugitive accelerators may be included in theaccelerator compositions, but additional non-fugitive accelerators areexcluded. The exclusions in either aspect are beneficial because thepresence of any additional vulcanization accelerators or the use ofnon-fugitive accelerators increases the likelihood that an allergicreaction, particularly a Type IV allergic reaction, may occur in a userof an elastomeric article formed with the vulcanization composition.

Latex Dispersions and Elastomeric Articles

The vulcanization compositions of the present invention may be used toprepare latex dispersions. The latex dispersion may comprise anelastomer that may be selected from natural rubber, polyurethane,polybutadiene, polychloroprene (Neoprene), nitrile rubber, blockcopolymers of styrene and butadiene, block copolymers of styrene andisoprene, and polyisoprene. According to certain aspects, a particularlypreferred elastomer for use in the latex dispersions of the invention ispolychloroprene. These latex dispersions may comprise, in addition tothe elastomer and vulcanization composition, one or more differentnon-curing ingredients. The non-curing ingredients may include, but arenot limited to, antioxidants, stabilizers, plasticizers, anti-ozoneagents, pigments, and fillers. According to an aspect of the invention,when making the first elastomeric layer (base glove), the total solidscontent of the latex dispersion is in a range from about 20% to about45%. According to some aspects of the invention for preparing a coatingcomposition suitable for forming a second, third, fourth, etc.elastomeric layer (e.g., as described in U.S. Published Appl. No.2008/0190322 A1, which is incorporated herein by reference in itsentirety), the total solids content of the latex dispersion is adjustedso that it is in a range of from about 1% to about 20%, preferably fromabout 2% to about 17%, and more preferably from about 3% to about 15%.According to one aspect of the invention, the total solids content ofthe latex dispersion is about 5%. According to other aspects of theinvention for preparing a single layer glove, or the first elastomericlayer of a glove having two or more layers, the total solids content ofthe latex dispersion is generally in the range of from about 20% toabout 45%, preferably from about 25% to about 40%.

The latex dispersions of the present invention that contain an elastomerand vulcanization composition may be used in methods for preparingelastomeric articles such as gloves, specifically medical gloves, andmore specifically examination and surgical gloves. However, it isconsidered within the ability of those skilled in the art to preparealternative elastomeric articles other than gloves, including, but notlimited to, condoms, probe covers, dental dams, finger cots, catheters,and the like, using the guidance provided herein.

The elastomeric articles of the present invention that are formed usingthe vulcanization compositions and/or latex dispersions described abovemay be produced using any conventional manufacturing methods, e.g.,coagulant dipping. In the “anode” coagulant-dipping process, acoagulant-coated former is dipped into the dispersion, and is then curedto form a finished article. In the “Teague” coagulant-dipping process,the former is dipped into the dispersion, and is then dipped into acoagulant, followed by curing to form a finished article. These methodsutilize dispersions containing the elastomer from which the finishedarticle is to be formed. Preferred elastomers include natural rubber,polyurethane, polybutadiene, polychloroprene (Neoprene), nitrile rubber,block copolymers of styrene and butadiene, block copolymers of styreneand isoprene, and polyisoprene. According to certain aspects, aparticularly preferred elastomer is polychloroprene. According to stillfurther aspects, a polychloroprene elastomeric article is provided thatis vulcanized using an vulcanization composition consisting of sulfur,zinc oxide, and DIXP.

In prior art compositions, DIXP has always been used in combination withadditional accelerators including non-fugitive accelerators, because itis not sufficiently active on its own to form adequate numbers of sulfurcrosslinks to form a useful elastomeric article. However, the presentinvention has unexpectedly discovered that it is possible to vulcanizepolychloroprene latex with a vulcanization composition consisting ofsulfur, DIXP, and zinc oxide in order to obtain an elastomeric articlehaving a tensile strength that meets the ASTM D6977-04 requirements forpolychloroprene examination gloves (minimum 14 MPa), as well as the ASTMD3577-01 requirements for synthetic latex surgical gloves (minimum 17MPa). Because DIXP is a fugitive xanthate, and no DIXP residue remainson the gloves following vulcanization, the gloves produced using thisvulcanization composition exhibit low allergenic potential.

Polychloroprene rubber can form crosslinks between polymer chains in thepresence of a catalyst, such as zinc oxide, magnesium oxide, or leadoxide, unlike natural rubber or synthetic polyisoprene rubber. Withoutwishing to be bound by theory, this crosslinking is believed to occur asa result of a bis-alkylation mechanism that is specific topolychloroprene due to its chemical structure. The crosslinking betweenpolymer chains is believed to take place at sites on the polymer chainwhere there are reactive tertiary allylic chlorine atoms formed by1,2-polymerization of chloroprene monomers. The labile chlorine amountsto about 1.5% of the total chlorine in the polychloroprene polymers. Inaddition to this type of crosslinking, it is also possible that sulfurcrosslinking could occur at other sites on the polymer chain. See Carl,Neoprene Latex, chapter 3.

The elastomeric articles of the present invention may be formed usinglatex dispersions containing any additives components that may be usedin forming the elastomeric articles, which may include at least one ofcuring ingredients, non-curing ingredients, and additional polymers, tobe discussed below, with the same, similar or different chemicalstructures from the elastomer. The total amount of additive(s) used isabout 0.5-49% by weight of total dispersion phase solids.

When curing using sulfur, the main curing agent preferably compriseselemental sulfur and/or a sulfur donor that has low or no allergenicpotential. According to certain aspects of the invention, only elementalsulfur is used.

Activators may include, but are not limited to, zinc oxide, magnesiumoxide, and lead oxide. Zinc oxide is the most commonly usedvulcanization activator.

Vulcanization accelerators in accordance with the invention are fugitivexanthates. According to further aspects of the invention, the fugitivexanthate is diisopropyl xanthogen polysulfide (DIXP) or a dialkylxanthogen disulfide, such as dibutyl xanthogen disulfide, anddiisopropyl xanthogen disulfide.

Any non-curing ingredients that are conventionally used in elastomerdispersion compounding formulations may be used in the presentinvention. For example, the non-curing ingredients may include, but arenot limited to, antioxidants, stabilizers, plasticizers, anti-ozoneagents, pigments, and fillers.

Suitable antioxidants that may be added to the elastomer dispersioninclude, but are not limited to, hindered phenols such as butylatedhydroxytoluene (2,6-di-tert-butyl-4-methylphenol) and thiodiethylenebis-di-t-butyl-4-hydroxyphenyl propionate, hindered polyphenolics suchas butylated reaction products of p-cresol and dicyclopentadiene,hindered phenol/hindered polyphenolics such as trimethyl-tris(di-t-butyl-4-hydroxybenzym)-benzene or octadecyldi-t-butyl-4-hydroxyphenyl propionate, amines such as a blend of 6PPDwith methyl styrene and bis-alpha-dimethylbenzyl diphenyl amine,mixtures such as zinc mercaptotulumimidazole/phenolic, triazinonederivatives such as triazinone-phenol mixtures, polyaromatic amines suchas poly(m-anisidine), phenolic antioxidant hydrazides such as phenolicswith anhydride copolymer, phenolics such as2,2′-methylene-bis-(4-methyl-6-t-butylphenol), cresols such as2,4-dimethyl-6-(1-methylcyclohexyl)-p-cresol, and styrenated phenols.One particularly preferred antioxidant is butylated reaction products ofp-cresol and dicyclopentadiene (e.g., Wingstay L).

Colloidal stabilizers including alkalis for pH adjustment, surfactantsand alkaline caseinates such as sodium caseinate may also be added tothe aqueous phase.

Suitable plasticizers that may be added to the elastomer dispersion mayinclude, but are not limited to, fatty salts, mineral oils and esterplasticizers.

According to some aspects, an antiozonant is added to an elastomerdispersion that is used to make the elastomeric articles of theinvention. Ozone can severely damage some elastomeric articles, such asthose formed from polymers that are highly unsaturated, likepolyisoprene. When included in the aqueous elastomer dispersion of theinvention, certain high molecular weight polymers, such as waxes, EPDMand hydrogenated polydiene can provide such articles with excellentozone resistance. Waxes form a physical barrier at the surface of therubber which protects against ozone attack. There are two types ofwaxes: straight chain paraffin waxes and branched-chain microcrystallinewaxes. The most widely used antiozonant waxes are blends of paraffin andmicrocrystalline waxes for maximum protection over a broad range ofexposure temperatures. Paraffin waxes are straight-chain hydrocarbonmolecules containing about 20 to 50 carbon atoms. Suitable paraffinwaxes have a melting point of from about 50 to 75° C., preferably 52 to68° C. Microcrystalline waxes are also known as amorphous waxes and arehydrocarbons, similar to paraffin waxes, but the carbon chains arebranched and have higher molecular weight of about 40 to 70 carbon atomsper chain. Other examples of antiozonants that may be used in theinvention may include, but are not limited to, alkyl/arylp-phenylenediamines such asN-1,3-dimethylbutyl-N′-phenyl-p-phenylenediamine 6PPD,organoclay-antiozonant complexes such as smectite-containing clay withalkyl-aryl-p-phenylenediamine, functionalized benzotriazoles such asN,N-disubstituted para-phenylenediamine, triazines such as tris(N-1,4-dimethylpentyl-p-phenylenediamino) 1,3,5-triazine and tris(N-alkyl-p-phenylenediamino) 1,3,5-triazine, and p-phenylenediaminessuch as N-isopropyl-N′-phenyl-p-phenylenediamine (IPPD). In addition,polymers including waxes such as paraffinic wax (MW=300-500),microcrystalline wax (MW=600-700) (with paraffinic wax) and low MW PEwax (MW=100-1100), polymeric antiozonants such as polymericdiphenyldiamine, and ozone inert polymers such as EPDM and brominatedisobutylene/para-methylstyrene copolymer (BIMSM) may be used asantiozonants. It is preferred that waxes are used. Once particularlypreferred wax is Michem Lube 180. Another preferred wax dispersion isAntilux 600.

Suitable pigments that may be added to the aqueous elastomer dispersionmay include a wide range of natural pigments such as titanium dioxideand iron oxides, and synthetic pigments.

Suitable fillers that may be added to the aqueous elastomer dispersionmay include, but are not limited to, inorganic fillers such as clays,calcium carbonate, talc, and silica and organic fillers such ascrosslinked polymethyl methacrylate, finely divided urethane resinparticles and polyethylene microspheres.

Additional polymers may also be incorporated into the latex dispersionsand elastomeric articles of the present invention. This may be done toprovide additional functionality or impart beneficial properties to thelatex dispersions and elastomeric articles. Such functions/propertiesmay include, but are not limited to, improved damp/wet donning, improvedfluid repellency, improved resistance to microorganisms, improvedresistance to degradation, etc. According to some aspects of theinvention, the additional polymer is selected from natural rubber,polyurethane, polybutadiene, polychloroprene (Neoprene), nitrile rubber,block copolymers of styrene and butadiene, block copolymers of styreneand isoprene, and polyisoprene. When present, the additional polymer maybe provided in an amount that is from about 5% to about 200% of theprimary polymer, preferably from about 25% to about 150%, morepreferably from about 50% to about 125%, and still more preferably fromabout 75% to about 100%. One exemplary latex dispersion containingadditional polymers includes 2.5% polychloroprene, 2.5% syntheticpolyisoprene, and 95% water (i.e., the additional polymer, polyisoprene,is provided in an amount that is 100% of the amount of the primarypolymer, polychloroprene). Another exemplary latex dispersion containingadditional polymers includes 2.5% polychloroprene, 2.5% nitrile, and 95%water.

According to some aspects of the invention, elastomeric articles areprovided that include multiple elastomeric layers, where the multipleelastomeric layers may have the same or different compositions. Forexample, a coating comprising synthetic polyisoprene blended withpolychloroprene may be applied to a polychloroprene elastomeric articleto provide improved damp/wet donning characteristics to the article. Inanother example, a coating composition comprising nitrile blended withpolychloroprene may be applied to a polychloroprene elastomeric articleto provide improved damp/wet donning characteristics to the article.

According to further aspects of the invention, the elastomeric articlesmay be formed either with, or without, powder or starch. Although powderand starch are commonly-used donning agents, they could be alsoassociated with allergic reactions, and therefore another aspect of theinvention relates to powder-free and starch-free elastomeric articles.Further aspects relate to substantially power-free and starch-freeelastomeric articles in which less than 5 mg of powder or starch,preferably less than 3 mg of powder or starch, more preferably less than2 mg of power or starch, and most preferably less than 1 mg of powder orstarch. These articles are prepared using the vulcanization compositionsdescribed above.

These and other aspects of the invention are further described in thenon-limiting Examples set forth below.

EXAMPLES Example 1—Commercial Powder-Free Polychloroprene Gloves

A commercially available powder-free polychloroprene surgical glove(Duraprene SMT by Cardinal Health) is formed using a vulcanizationcomposition comprising sulfer, zinc dibutyl dithiocarbamate, and zincoxide. The unaged and aged properties of the gloves are shown in Table1.

TABLE 1 Physical Properties of Powder-Free Duraprene SMT Gloves Aged (7days, Properties Unaged 70° C.) Tensile Strength, MPa 19.6 19.1 TensileStress @ 500%, MPa 1.86 — Ultimate Elongation, % 1003 888

Example 2—Preparation of Powdered Gloves

Polychloroprene latex was compounded using a formulation comprisingeither Formulation A (comparative formulation), which includes only zincoxide as curing agent, or Formulation B, which includes a combination ofsulfur, zinc oxide, and DIXP as curing agent. The complete compoundingformulations are set forth in Table 2.

TABLE 2 Compounding Formulations Parts per weight Parts per weight dryrubber (phr) dry rubber (phr) Ingredient Formulation A Formulation BNeoprene 750 Latex 100.00 100.00 Darvan SMO Solution 4.50 4.50 DarvanWAQ Solution 1.50 1.50 Uniflo 26 Solution 0.50 0.50 Zinc OxideDispersion 12.00 12.00 Sulfur Dispersion 0.00 1.50 Robac AS100 (DIXP)0.00 2.00 Wingstay L 0.75 0.75 Michemlube 180 1.00 1.00 Rodo # 0 0.0280.028 Triton X-100 0.013 0.013 Titanium Dioxide 0.200 0.200 DispersionPigment 0.080 0.080

Gloves were formed by the standard coagulant dipping process, and werevulcanized using hot air. The properties of the gloves are shown inTable 3.

TABLE 3 Physical Properties of Polychloroprene Gloves PropertiesFormulation A Formulation B Tensile Strength, MPa 12.00 23.00 TensileStress @ 300%, MPa 0.88 1.47 Tensile Stress @ 500%, MPa 1.08 2.55Ultimate Elongation, % 1160 904

The gloves cured only with zinc oxide exhibited a tensile strength of 12MPa, which was not sufficient to meet ASTM requirements for eitherexamination or surgical gloves. However, the inventive gloves cured witha combination of sulfur, zinc oxide, and DIXP exhibited a tensilestrength of 23 MPa, which exceeded the ASTM requirements forpolychloroprene examination gloves and surgical gloves made fromsynthetic latex.

Example 3—Preparation of Powder-Free Gloves

Powder-free polychloroprene gloves were prepared by forming a base glovelayer using the standard coagulant dipping process, and using thecompounded latex of Formulation B or the compounded latex of FormulationC. The latex formulations are set forth below in Table 4.

TABLE 4 Compounding Formulation Parts per weight Parts per weight dryrubber (phr) dry rubber (phr) Ingredient Formulation B Formulation CNeoprene 750 Latex 100.00 100.00 Darvan SMO Solution 4.50 4.50 DarvanWAQ Solution 1.50 1.50 Uniflo 26 Solution 0.50 0.50 Zinc OxideDispersion 12.00 6.00 Sulfur Dispersion 1.50 1.20 Robac AS100 (DIXP)2.00 3.00 Wingstay L 0.75 0.75 Michemlube 180 1.00 1.00 Rodo # 0 0.0280.028 Triton X-100 0.013 0.013 Titanium Dioxide 0.200 0.200 DispersionPigment 0.080 0.080

The former bearing the wet base glove layer was then leached in water,and after partial drying was dipped into a blend of compoundedpolychloroprene latex and nitrile latex so as to form a thin coating ofthe latex blend onto the base glove layer. The rubber latex blendcomprised about 2.5% compounded polychloroprene latex and 2.5% nitrilelatex, and about 95% water. Formulations B and C were used as theformulation for the blend of compounded polychloroprene latex withnitrile latex. For example, if Formulation B compounded polychloroprenelatex is used for dipping the base polychloroprene glove, then a coatingcomposition having 5% total solids content would contain a blend of 2.5%Formulation B compounded polychloroprene latex and 2.5% raw nitrilelatex. Similarly, if Formulation C compounded polychloroprene latex isused for dipping the base polychloroprene glove, then a coatingcomposition having 5% total solids content, the coating compositionwould contain, for example, a blend of 2.5% Formulation C compoundedpolychloroprene latex and 2.5% raw nitrile latex. While generally it isconvenient for the coating composition to use a blend of raw nitrilelatex and compounded polychloroprene latex using the same compoundingformulation as that used for the polychloroprene latex for making thebase glove, it is possible that the compounding formulations for thebase glove and the coating layer be different. For example, it ispossible to use Formulation C for making the base glove and FormulationB to blend with raw nitrile latex for coating the base glove.

The former was withdrawn from the latex blend, dried, and thenvulcanized in a hot air oven at temperatures of from about 120° C. toabout 155° C. After vulcanization, the glove was stripped from theformer so that the coated surface was on the inside of the glove. Theglove was then turned inside-out so that the coated surface was on theoutside of the glove, and was post-processed by chlorination. Thechlorination consisted of prewashing the glove with water beforechlorination in an aqueous chlorine solution containing about 300 ppmavailable chlorine, neutralizing any excess chlorine with sodiumhydroxide solution, followed by further washing with water (this stepwas carried out several times). The glove was then partially dried andthen manually inverted again and dried further.

For good donning with wet or damp hands, the gloves were transferred toa tumbling washer for a further lubrication process following thechlorination step. This lubrication process included tumbling the gloveswith an aqueous solution comprising about 1.0% cetylpyridium chloride,1.0% silicone emulsion, and 1.5% ammonium salts of alkyl phosphates. Theglove was removed from the tumbler washer, partially dried, and manuallyinverted. The glove was then dried further. The treated glove could beeasily donned by dry or damp hands.

The properties of the coated powder-free gloves of Formulations B and Care set forth in Tables 5 and 6.

TABLE 5 Physical Properties of Coated Powder-Free Polychloroprene GlovesFormulation B Properties Unaged *Aged Maturation = 1 day TensileStrength, MPa 24.0 27.6 Tensile Stress @ 300%, MPa 1.47 1.76 TensileStress @ 500%, MPa 2.25 2.84 Ultimate Elongation, % 1002 924 Maturation= 3 days Tensile Strength, MPa 23.8 27.2 Tensile Stress @ 300%, MPa 1.371.76 Tensile Stress @ 500%, MPa 2.16 2.94 Ultimate Elongation, % 1111865 Maturation = 5 days Tensile Strength, MPa 22.5 24.5 Tensile Stress @300%, MPa 1.27 1.27 Tensile Stress @ 500%, MPa 1.96 2.45 UltimateElongation, % 1120 884 *Aging conditions were 7 days at 70° C.

TABLE 6 Physical Properties of Coated Powder-Free Polychloroprene GlovesFormulation C Properties Unaged *Aged Maturation = 2 days TensileStrength, MPa 17.8 19.2 Tensile Stress @ 300%, MPa 0.98 1.37 TensileStress @ 500%, MPa 1.37 2.06 Ultimate Elongation, % 1120 924 Maturation= 3 days Tensile Strength, MPa 21.6 21.4 Tensile Stress @ 300%, MPa 1.281.47 Tensile Stress @ 500%, MPa 1.86 2.84 Ultimate Elongation, % 963 924*Aging conditions were 7 days at 70° C.

It was seen that the coated powder-free gloves of Formulation B had goodphysical properties both before aging and after accelerated aging for 7days at 70° C. The tensile strength values for the unaged gloves ofFormulation B made from latex that was matured for 1, 3, or 5 days wereall greater than 22 MPa, and after accelerated aging, the tensilestrength values were all greater than 24 MPa. These values exceeded theASTM requirements for polychloroprene examination gloves and surgicalgloves made from synthetic latex.

The tensile strength values for the unaged coated powder-free gloves ofFormulation C made from latex that was matured for 2 or 3 days wereapproximately the same as the commercial powder free gloves ofExample 1. Therefore, the results of shown in Tables 5 and 6 demonstratethat the vulcanization composition can be varied to yield gloves thatcan meet ASTM requirements for surgical gloves and examination gloves.

Example 4—Preparation of Powder-Free Gloves

Powder-free coated polychloroprene gloves were prepared as describedabove in Example 3, with the exception that the latex blend used forcoating comprised about 2.5% compounded polychloroprene latex, about2.5% synthetic polyisoprene latex, and about 95% water.

The properties of the resulting gloves were similar to those of thegloves prepared in Example 3.

Example 5—Residual DIXP

Powdered polychloroprene gloves and powder-free polychloroprene gloveswere prepared using Formulation B as described in Example 2 and Example3 (but without the lubrication process). The gloves were tested forresidual DIXP using UV spectroscopy. The gloves were extracted withhexane as well as acetonitrile and UV spectra of the extracts wereobtained. The UV spectra of both the extracts showed that there was noresidual DIXP remaining in either of the powdered or powder-free gloves.The UV spectroscopy testing method has detection limit of 1 ppm.

It will, of course, be appreciated that the above description has beengiven by way of example only and that modifications in detail may bemade within the scope of the present invention.

Throughout this application, various patents and publications have beencited. The disclosures of these patents and publications in theirentireties are hereby incorporated by reference into this application,in order to more fully describe the state of the art to which thisinvention pertains.

The invention is capable of considerable modification, alteration, andequivalents in form and function, as will occur to those ordinarilyskilled in the pertinent arts having the benefit of this disclosure.

While the present invention has been described for what are presentlyconsidered the preferred embodiments, the invention is not so limited.To the contrary, the invention is intended to cover variousmodifications and equivalent arrangements included within the spirit andscope of the detailed description provided above.

We claim:
 1. A vulcanization composition comprising: a source of sulfur,a single fugitive xanthate accelerator, and a metal oxide, where thecomposition does not include any additional compounds that function asaccelerators for vulcanizing elastomers.
 2. The vulcanizationcomposition of claim 1, wherein the sulfur is elemental sulfur andwherein the single fugitive xanthate accelerator is diisopropylxanthogen polysulfide.
 3. The vulcanization composition of claim 1,wherein the vulcanization composition exhibits reduced allergenicity ascompared to conventional vulcanization compositions.
 4. Thevulcanization composition of claim 1, wherein the metal oxide isselected from the group consisting of zinc oxide, magnesium oxide, leadoxide, and combinations thereof.
 5. The vulcanization composition ofclaim 1, wherein the source of sulfur is selected from the groupconsisting of elemental sulfur and sulfur donors that have a lowallergenic potential, and combinations thereof.
 6. The vulcanizationcomposition of claim 1, wherein the single fugitive xanthate acceleratoris selected from the group consisting of diisopropyl xanthogenpolysulfide, dibutyl xanthogen disulfide, and diisopropyl xanthogendisulfide.
 7. The vulcanization composition of claim 1, wherein thecomposition does not contain any additional xanthate compounds.
 8. Anelastomeric article formed using the vulcanization composition of claim1, where the elastomeric article does not include any additionalcompounds that function as accelerators for vulcanizing elastomers. 9.The elastomeric article of claim 8, wherein the elastomeric articleexhibits reduced allergenicity as compared to elastomeric articlesformed using conventional accelerators.
 10. The elastomeric article ofclaim 8, wherein the elastomeric article is selected from the groupconsisting of gloves, probe covers, finger cots, catheters, dental dams,and condoms.
 11. The elastomeric article of claim 8, wherein theelastomeric articles are powder free.
 12. A vulcanization compositioncomprising: a source of sulfur, a single fugitive xanthate accelerators,and a metal oxide, wherein the composition does not include anynon-fugitive accelerators; and wherein the composition does not includeany additional xanthate compounds.
 13. The vulcanization composition ofclaim 12 wherein the source of sulfur is elemental sulfur anddiisopropyl xanthogen polysulfide is the single fugitive xanthateaccelerator.
 14. The vulcanization composition of claim 12, wherein thevulcanization composition exhibits reduced allergenicity as compared toconventional vulcanization compositions.
 15. The vulcanizationcomposition of claim 12, wherein the metal oxide is selected from thegroup consisting of zinc oxide, magnesium oxide, lead oxide, andcombinations thereof.
 16. The vulcanization composition of claim 12,wherein the source of sulfur is selected from the group consisting ofelemental sulfur and sulfur donors that have a low allergenic potential,and combinations thereof.
 17. The vulcanization composition of claim 12,wherein the single fugitive xanthate accelerator is selected from thegroup consisting of diisopropyl xanthogen polysulfide, dibutyl xanthogendisulfide, and diisopropyl xanthogen disulfide.
 18. An elastomericarticle formed using the vulcanization composition of claim 12, wherethe elastomeric article does not include any non-fugitive accelerators.19. The elastomeric article of claim 18, wherein the elastomeric articleexhibits reduced allergenicity as compared to elastomeric articlesformed using conventional accelerators.
 20. The elastomeric article ofclaim 18, wherein the elastomeric article is selected from the groupconsisting of gloves, probe covers, finger cots, catheters, dental dams,and condoms.
 21. The elastomeric article of claim 18, wherein theelastomeric articles are powder free.